Rapid analysis of the essential oils from dried Illicium verum Hook. f. and Zingiber officinale Rosc. by improved solvent-free microwave extraction with three types of microwave-absorption medium

A new method of extracting essential oils from dried plant materials has been studied. By adding a microwave-absorption medium (MAM) to a reactor, solvent-free microwave extraction (SFME) was improved and can be used to extract essential oils from dried plant material without pretreatment. With a microwave irradiation power of 85 W it took only approximately 30 min to extract the essential oils completely. The whole extraction process is simple, rapid, and economical. Three types of MAM, iron carbonyl powder (ICP), graphite powder (GP), and activated carbon powder (ACP), and two types of dried plant material, Illicium verum Hook. f. and Zingiber officinale Rosc., were studied. The results were compared with those obtained by use of conventional SFME, microwave-assisted hydrodistillation (MAHD), and conventional hydrodistillation (HD), and the conclusion drawn was that improved SFME was a feasible means of extracting essential oils from dried plant materials, because there were few differences between the composition of the essential oils extracted by improved SFME and by the other methods.     

Kinetic Study of Microwave Extraction of Essential Oil of Nigella sativa L. Seeds

The Nigella sativa L. is widely cultivated in the Algerian Sahara and primarily used for its health benefits. Extraction experiments were carried out by a microwave energy, performed at atmospheric pressure with a small quantity of water for 10 min. This method enabled a best yield (0.54–0.57%) and a high amount of the volatile fraction with a shorter extraction time and a reduction of energy consumption. The kinetic study of essential oils extraction was quantitatively studied. Thus, the qualitative and quantitative composition of the essential oils extracted for 10 min and in different periods was examined by capillary gas chromatography and by gas chromatography-mass spectrometry. The percentage of the main constituents such as p-cymene, thymoquinone, α-thujene, 4-terpineol and carvacrol was reported. The family classes present a significant variation according to the extraction time. Kinetic and extraction rate profile of microwave process (yield) showed that it is possible to reduce the extraction time.     

Non-polar Solvent Microwave-Assisted Extraction of Volatile Constituents from Dried Zingiber Officinale Rosc.

A new method, non-polar solvent microwave-assisted extraction （NPSMAE）, was applied to the extraction of essential oil from Zingiber officinale Rosc. in closed-vessel system. By adding microwave absorption mediumcarbonyl iron powders （CIP） into extraction system, the essential oil was extracted by the non-polar solvent （ether） which can be heated by CIP. The constituents of essential oil obtained by NPSMAE were comparable with those obtained by hydrodistillation （HD） by GC-MS analysis, which indicates that NPSMAE is a feasible way to extract essential oil from dried plant materials. The NPSMAE took much less extraction time （5 min） than HD （180 min）, and its extraction efficiency was much higher than that of conventional polar solvent microwave-assisted extraction （PSMAE） and mixed solvent microwave-assisted extraction （MSMAE）. It can be a good alternative for the extraction of volatile constituents from dried plant samples.     

Headspace single drop microextraction coupled with microwave extraction of essential oil from plant materials

Headspace single drop microextraction (HS-SDME) coupled with microwave extraction (ME) was developed and applied to the extraction of the essential oil from dried Syzygium aromaticum (L.) Merr. et Perry and Cuminum cyminum L. The operational parameters, such as microdrop volume, microwave absorption medium (MAM), extraction time, and microwave power were optimized. Ten microliters of decane was used as the microextraction solvent. Ionic liquid and carbonyl iron powder were used as MAM. The extraction time was less than 7 min at the microwave power of 440 W. The proposed method was compared with hydrodistillation (HD). There were no obvious differences in the constituents of essential oils obtained by the two methods.     

Rapid Extraction of Essential Oil from Dried Cinnamomum cassia Presl and Forsythia suspensa(Thunb.)Vahl by Ionic Liquid Microwave Extraction

Ionic liquid (IL) was used as the microwave absorption medium to extract essential oils from dried Cinnamomum cassia Presl and Forsythia suspensa (Thunb.) Vahl, and the ionic liquid microwave extraction (ILME) was developed. Some experimental parameters for ILME were examined. The proposed method was compared with other methods, including hydrodistillation (HD), microwave hydrodistillation (MHD), solvent‐free microwave extraction (SFME) and improved solvent‐free microwave extraction (ISFME). Experimental results showed that compared with other extraction methods the ILME had some advantages, such as time‐saving, simplicity and usage of green solvents. The extraction time was less than 18 min at the microwave power of 440 W and 1.5 mL of ionic liquid was required. The constituents of essential oils obtained by the five methods are not obviously different.     

Rapid extraction and determination of 25 bioactive constituents in Alpinia oxyphylla using microwave extraction with ultra high performance liquid chromatography with tandem mass spectrometry

A novel and rapid microwave extraction and ultra high performance liquid chromatography with tandem mass spectrometry method was developed and validated for the simultaneous determination of 25 bioactive constituents (including two new constituents) in Fructus Alpinia oxyphylla. The optimized conditions of the microwave extraction was a microwave power of 300 W, extraction temperature of 80°C, solvent‐to‐solid ratio of 30 mL/g and extraction time of 8 min. Separation was achieved on a Waters ACQUITY UPLC^® HSS C₁₈ column (2.1 mm× 50 mm, 1.8 μm) using gradient elution with a mobile phase consisting of acetonitrile and 1 mM ammonium acetate at a flow rate of 0.2 mL/min. This is the first report of the simultaneous determination of 25 bioactive constituents in Fructus Alpinia oxyphylla by ultra high performance liquid chromatography with tandem mass spectrometry. The method was validated with good linearity, acceptable precision and accuracy. The validated method was successfully applied to determine the contents of 25 bioactive constituents in Fructus Alpinia oxyphylla from different sources and the analysis results were classified by hierarchical cluster analysis, which indicated the effect of different cultivation regions on the contents of constituents. This study provides powerful and practical guidance in the quality control of Alpinia oxyphylla and lays the foundation for further research of Alpinia oxyphylla.     

Solvent-free microwave extraction of essential oil from aromatic herbs: comparison with conventional hydro-distillation

Solvent-free microwave extraction (SFME) is a combination of microwave heating and dry distillation, performed at atmospheric pressure without added any solvent or water. Isolation and concentration of volatile compounds are performed by a single stage. SFME has been compared with a conventional technique, hydro-distillation (HD), for the extraction of essential oil from three aromatic herbs: basil (Ocimum basilicum L.), garden mint (Mentha crispa L.), and thyme (Thymus vulgaris L.). The essential oils extracted by SFME for 30min were quantitatively (yield) and qualitatively (aromatic profile) similar to those obtained by conventional hydro-distillation for 4.5 h. The SFME method yields an essential oil with higher amounts of more valuable oxygenated compounds, and allows substantial savings of costs, in terms of time, energy and plant material. SFME is a green technology and appears as a good alternative for the extraction of essential oils from aromatic plants.     

Effect of microwaves on the in situ hydrodistillation of four different Lamiaceae

The development of alternative techniques to classic hydrodistillation (HD) has been prompted because of the drawbacks of the more traditional technique. These drawbacks include: partial thermal degradation, high energy consumption and the fact that it is a time-consuming process. In situ microwave-generated hydrodistillation (MGH) and microwave hydrodiffusion and gravity (MHG) are suitable methods which may improve the preparation of essential oils. In this work, we report a comparison study of HD, MGH and MHG used in the extraction of four plant species cultivated in Piedmont (Italy): lavender, oregano, basil and sage. Both microwave-assisted procedures gave excellent results; in particular the essential oils obtained under MHG were very similar to those obtained with HD. In MGH, the polarity and the physico-chemical properties of the extracted compounds caused bigger differences in essential oil composition.     

Eco-friendly and cleaner process for isolation of essential oil using microwave energy: Experimental and theoretical study

Microwave steam diffusion (MSD) was developed as a cleaner and new process design and operation for isolation of essentials oils and was compared to conventional steam diffusion (SD). The essential oils extracted by MSD for 3 min were quantitatively (yield) and qualitatively (aromatic profile) similar to those obtained by conventional steam diffusion for 20 min. In addition, an optimal operating steam flow rate of 25 g min⁻¹ and microwave power 200 W were found to ensure complete extraction yield with reduced extraction time. To confirm the efficiency of this process a mathematical model was proposed to describe the mass transfer of essential oil from lavender. Solid-steam mass transfer coefficients obtained by MSD were six times higher than obtained by SD. Scanning electronic microscopy was used to confirm the extraction mechanism of the essential oil present in the glandular trichomes of the flowers from lavender outer surface. MSD was better than SD in terms of energy saving, cleanliness and reduced waste water.     

Comparative analysis of essential oil composition from flower and leaf of Magnolia kwangsiensis Figlar & Noot.

The essential oils from Magnolia kwangsiensis Figlar & Noot. were obtained using hydrodistillation, and analysed by GC and GC–MS. A total of 31, 27 and 26 constituents were identified in the oils from male flower, female flower and leaf of M. kwangsiensis, and they comprised 99.2, 98.5 and 96.2% of the oils, respectively. Monoterpene hydrocarbons predominated in the oils and accounted for 48.3% of male flower oil, 54.0% of female flower oil and 44.6% of leaf oil. The compositions of flower oils were quite similar but with different content, and were different from those of leaf oil.     

Analysis of essential oils from Voacanga africana seeds at different hydrodistillation extraction stages: chemical composition,antioxidant activity and antimicrobial activity

In this study, essential oils from Voacanga africana seeds at different extraction stages were investigated. In the chemical composition analysis, 27 compounds representing 86.69–95.03% of the total essential oils were identified and quantified. The main constituents in essential oils were terpenoids, alcohols and fatty acids accounting for 15.03–24.36%, 21.57–34.43% and 33.06–57.37%, respectively. Moreover, the analysis also revealed that essential oils from different extraction stages possessed different chemical compositions. In the antioxidant evaluation, all analysed oils showed similar antioxidant behaviours, and the concentrations of essential oils providing 50% inhibition of DPPH-scavenging activity (IC₅₀) were about 25 mg/mL. In the antimicrobial experiments, essential oils from different extraction stages exhibited different antimicrobial activities. The antimicrobial activity of oils was affected by extraction stages. By controlling extraction stages, it is promising to obtain essential oils with desired antimicrobial activities.     

Microwave accelerated steam distillation of essential oil from lavender: A rapid, clean and environmentally friendly approach

A new process design and operation for microwave accelerated steam distillation (MASD) of essential oils was developed. A packed bed of lavender flowers (Lavandula angustifolia Mill., Lamiaceae) sits above the steam source generated by microwave heating. Only steam passes through it without the boiling water mixing with vegetable raw material, as is the case in hydro-distillation. MASD has been compared with a conventional technique, steam distillation (SD), for the extraction of essential oil from lavender flowers. Extraction of essential oils from lavender with MASD was better than SD in terms of energy saving, rapidity (10 min versus 90 min), product yield, cleanliness and product quality.     

离子液体-非极性溶剂微波提取法在人参化学成分研究中的应用

以离子液体作为微波吸收介质建立了离子液体-非极性溶剂微波提取法,对人参中的化学成分进行了提取,并将该法与固体微波吸收介质-非极性溶剂微波提取法、极性溶剂微波提取法以及混合溶剂微波提取法进行了对比.结果表明,极性溶剂提取的主要化学成分为极性化合物,而固体微波吸收介质-非极性溶剂微波提取法与离子液体-非极性溶剂微波提取法相比,提取所得的化学成分并无明显差别,说明离子液体是一种较好的微波吸收介质和能量传递材料.所建立的方法具有提取时间短、操作简单及绿色环保等优点,且对后期分析无明显影响,是快速提取化学成分的理想方法.     

Phytochemical Investigation by Microwave‐Assisted Extraction of Essential Oil of the Leaves of Walnut Cultivated in Algeria

Walnut (Juglans regia L.) leaves are used traditionally as an herbal tea indicated for non‐insulin‐dependent diabetics. In recent years, the type‐II diabetes is occurring worldwide with increasing frequency. Thus, there is an urgent need to explore the new beneficial biomolecules on the human health. Our objective was to investigate, for the first time, the volatiles profile of Juglans regia L. leaves from Algiers region. The extraction of essential oil of fresh plant material was performed by microwave‐assisted hydrodistillation (MAHD), for the first time, a relatively recent method, then by the conventional hydrodistillation technique (HD) for comparison. The collected extracts were analyzed by GC‐FID and GC/MS using two capillary columns with different polarity. Extraction time of 1 h by MAHD provided higher yields (0.050±0.001% (w/w)) than by HD (0.030±0.006% (w/w)) after 3 h. A total of 38 compounds were identified using both techniques. Essential oils had similar qualitative but different quantitative composition in terms of chemical compounds. The MAHD method improved yield while reducing the extraction time. The sesquiterpenes were the dominant family in both MAHD and HD essential oils with β‐caryophyllene being the major constituent. Monoterpenes, including hydrocarbon and oxygenated, prevail in HD volatile fraction with β‐pinene and eucalyptol, respectively, as major components.     

Solvent-free microwave extraction and hydrodistillation of essential oils from endemic Origanum husnucanbaseri H. Duman, Aytac & A. Duran: comparison of antibacterial activity and contents

The essential oils (EOs) obtained by solvent-free microwave extraction (SFME) and hydrodistillation (HD) from endemic Origanum husnucanbaseri H. Duman, Aytac & A. Duran were investigated using the gas chromatography-mass spectrometry system. The main constituents of both oils obtained from SFME and HD from O. husnucanbaseri are borneol (15.2-12.8%), α-terpineol (12.3-10.8%) and trans-sabinene hydrate (11.8-9.92%). The EO obtained from SFME contained substantially higher amounts of oxygenated compounds and lower amounts of monoterpenes than that from HD. The antibacterial activities of the EOs from SFME and HD were evaluated by the disc diffusion method against six bacterial strains. The EO extracted by SFME was more effective than the EO extracted by HD against the tested bacteria, except for Klebsiella pneumoniae American type culture collection (ATCC) 13883. Streptococcus pyogenes ATCC 19615 and Staphylococcus aureus ATCC 25923 in particular were more sensitive against the EO extracted by SFME.     

Advanced analytical techniques for the extraction and characterization of plant‐derived essential oils by gas chromatography with mass spectrometry

In recent years, essential oils have received a growing interest because of the positive health effects of their novel characteristics such as antibacterial, antifungal, and antioxidant activities. For the extraction of plant‐derived essential oils, there is the need of advanced analytical techniques and innovative methodologies. An exhaustive study of hydrodistillation, supercritical fluid extraction, ultrasound‐ and microwave‐assisted extraction, solid‐phase microextraction, pressurized liquid extraction, pressurized hot water extraction, liquid–liquid extraction, liquid‐phase microextraction, matrix solid‐phase dispersion, and gas chromatography (one‐ and two‐dimensional) hyphenated with mass spectrometry for the extraction through various plant species and analysis of essential oils has been provided in this review. Essential oils are composed of mainly terpenes and terpenoids with low‐molecular‐weight aromatic and aliphatic constituents that are particularly important for public health.     

微波提取对挥发油化学成分的影响

采用无溶剂微波辅助提取与微波水蒸气蒸馏法提取薄荷叶和花椒挥发油,气相色谱-质谱(GC-MS)分析挥发油化学成分,与传统的水蒸气蒸馏对比,考察了微波对挥发油化学成分的影响.结果表明,微波促使薄荷叶挥发油中的薄荷醇氧化,转变为长叶薄荷酮和少量的薄荷呋喃酮.花椒挥发油中的按油素等化合物受质子的催化,在长时间温度较高的提取条件...     

Comparison of MAHD with UAE and Hydrodistillation for the Analysis of Volatile Oil From Four Parts of Perilla frutescens Cultivated in Southern China

Three different isolation techniques, specifically microwave-assisted hydrodistillation (MAHD), ultrasound-assisted extraction (UAE), and conventional hydrodistillation (HD) were employed to obtain essential oils from whole plants, leaves, roots, and stems of Perilla frutescens. The essential oils were analyzed using gas chromatography with flame ionization detection and gas chromatography with mass spectrometry. Variations in chemical composition were observed; these were attributed to differences in plant organs. Variations in the percentages of the main constituents of the oils extracted based on plant organ were irregular and affected the quantity and composition of the oils. Oil yields were affected by the method of extraction and extraction organ variation. The maximum volume of oil was extracted from leaves via MAHD and the minimum was extracted from roots via UAE. Oil yields ranged from 0.05% to 0.53%. The contents of essential oil varied significantly with the plant organ. In the essential oils of the plant parts studied were showed a predominance of oxygenated monoterpenes. Variation of extraction methods and organs may influence the oil components either qualitatively or quantitatively.     

Rapid analysis of the essential oil components of dried Zanthoxylum bungeanum Maxim by Fe2O3‐magnetic‐microsphere‐assisted microwave distillation and simultaneous headspace single‐drop microextraction followed by GC–MS

In this work, microwave distillation assisted by Fe₂O₃ magnetic microspheres (FMMS) and headspace single‐drop microextraction were combined, and developed for determination of essential oil compounds in dried Zanthoxylum bungeanum Maxim (ZBM). The FMMS were used as microwave absorption solid medium for dry distillation of dried ZBM. Using the proposed method, isolation, extraction, and concentration of essential oil compounds can be carried out in a single step. The experimental parameters including extraction solvent, solvent volume, microwave power, irradiation time, and the amount of added FMMS, were studied. The optimal analytical conditions were: 2.0 μL decane as the extraction solvent, microwave power of 300 W, irradiation time of 2 min, and the addition of 0.1 g FMMS to ZBM. The method precision was from 4 to 10%. A total of 52 compounds were identified by the proposed method. The conventional steam distillation method was also used for the analysis of essential oil in dried ZBM and only 31 compounds were identified by steam distillation method. It was found that the proposed method is a simple, rapid, reliable, and solvent‐free technique for the determination of volatile compounds in Chinese herbs.     

Chemical composition and antibacterial activity of Origanum saccatum P.H. Davis essential oil obtained by solvent-free microwave extraction: comparison with hydrodistillation

The components of the essential oils (EOs) obtained by solvent-free microwave extraction (SFME) and hydrodistillation (HD) from endemic Origanum saccatum P.H. Davis were identified by using GC/MS. The main constituents of both EOs obtained by SFME and HD, respectively, from O. saccatum were p-cymene (72.5 and 70.6%), thymol (9.32 and 8.11%), and carvacrol (7.18 and 6.36%). The EO obtained by SFME contained substantially higher amounts of oxygenated compounds and lower amounts of monoterpenes than did the EO obtained by HD. The antibacterial activities of the EOs obtained by SFME and HD were evaluated with the disc diffusion method by comparison with 10 different bacterial strains. The antibacterial activity of the EO extracted by SFME was found to be more effective than that of the EO extracted by HD against seven of the tested bacteria.